I just received the Arduino Cookbook in the mail today, and spent this sunny (hot, muggy) afternoon resting on the sofa and perusing its pages.  I got it in particular for support in Networking with Arduino, and was pleased to find that this book includes a section on working with Pachube, handling server requests, etc. It’s not necessarily for beginners; see “Getting Started with Arduino” from the O’Reilly series instead.  Note: the cookbook does not include any information on the Lilypad Arduino.

Note: I found this very detailed review of the book online.